One-step preparation of FexOy/N-GN/CNTs heterojunctions as a peroxymonosulfate activator for relatively highly-efficient methylene blue degradation

Persulfate decontamination technologies utilizing radical-driven processes are powerful tools for the treatment of a broad range of impurities. However, the design of high-performance catalytic activators with multi-functionality remains a great challenge. Therefore, in this study, three-dimensional multifunctional FexOy/N-GN/CNTs (N-GN: nitrogen-doped graphene, CNTs: carbon nanotubes) heterojunctions, which can be employed as microwave absorbers and catalysts, were synthesized via a solvothermal method and applied to activate peroxymonosulfate for the degradation of methylene blue (MB). X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscope (SEM), and X-ray photoelectron microscopy (XPS) analyses revealed that the FexOy were anchored in-situ onto the N-GN network. Using MB as the model organic dye, various factors, such as degradation systems, PMS loading, initial organic pollutant concentration, and catalyst dosage were optimized. The results revealed that the remarkable efficiency was attributable to the synergistic effects of carbon, nitrogen, and iron-based species. The oxidation system corresponded to the pseudo-first-order kinetic with a k value of similar to 0.33 min(-1). It was demonstrated that both SO4 center dot- and OH center dot were the predominant reactive species through quenching experiments. Because these heterojunctions were employed as microwave absorbers and have a semiconductor-like texture, the Fe/N co-rich hierarchical porous carbon skeleton favored electron transport and storage. These heterojunctions increase the options for transitional metal catalysts and highlights the importance of designing other heterojunctions for specific applications, such as supercapacitors, energy storage, CO2 capture, and oxygen reduction electrocatalysts. (C) 2018, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.